Welcome to Ask Dave Arnold, a new regular feature in which David Arnold, director of technology at the French Culinary Institute, provides in-depth answers to reader questions on food science, cooking technique, and other issues. If you'd like to send in a query, do e-mail it in. To this week's batch:
[Original artwork by Eric Lebofsky]
Question One: What would be the best way to use transglutaminase to make meatballs with no other binder?
Dave Arnold: For those of you not in-the-know, transglutaminase, aka meat glue or TG, is a naturally occurring enzyme that bonds proteins together. For very silly reasons, it has been controversial lately (see my feelings on the subject here).
Testing meat glue: the three-step process.
The primary binder in meatballs isn’t egg, or any other added ingredient, but salt. When you salt meat and knead it, proteins in the meat become soluble. That soluble protein gels when the meatball is cooked, binding it firmly together. If you make a traditional meatball and add TG, that meat gel becomes way too strong and the meatball becomes rubbery. I can make a meatball into a ping-pong ball this way.
If you want to make a low salt meatball, TG is a very good option. Just mix the TG with the meat mixture right before you form the meatballs. The amount you use will depend on how much salt is in the mix. If you add no salt, you may use up to 1 percent by weight of Activa RM (the brand of meat glue most chefs use). If you add some salt, use less meat glue.
After you add the TG, you have 20 minutes to form your meatballs. The TG then needs to set. Setting will take 4 hours in the fridge. The problem is, if you added some salt to the mix, that 4 hour rest is going to “cure” the meat a bit, altering its color and texture. If you have the equipment, I would poach the meatballs in butter held at 55 degrees Celsius for 25 minutes. That will set the TG. After the poach, cook as you wish.
Question Two: I'm working on a barbecue sauce for competitions. I'm starting out with onions and garlic sauteed in mangalista lard (about 1/4 cup for the recipe). Then I'm stirring in the spices and tomato paste for a few seconds before deglazing with bourbon and reducing. Finally I finish with my sugars, pork stock, and cider vinegar. This simmers for a few minutes and then I blend it and strain it to smooth it all out.
The problem I have is that the only emulsifier in it is a small amount mustard powder. As long as I keep it warm it tends to be ok, but as it cools in the fridge, the fat tends to rise and solidify on the top. Reheating and blending it back while on site at the competition is pretty difficult (power is not easy to come by). I'm trying to find some way to keep it from separating. I have a feeling that some combination of xanthan gum and/or lecithin would probably do it, but I don't want to add too much and mess with the texture a lot. What would be a good percentage of each to start with?
Dave Arnold: There are two separate ingredients you should use in tandem to solve your problem: an emulsifier and stabilizer. Emulsifiers are like marriage counselors: they make it easier for oil and water to exist side by side. Stabilizers are like traffic cops: they physically prevent the fat droplets from moving through the water, merging together, and floating to the top. Sometimes a single ingredient can both stabilize and emulsify, but it often makes sense to use two different products.
For your emulsifier, I would not recommend lecithin (a primary emulsifier in egg yolks) for several reasons:
· Soy lecithin can sometimes taste weird.
· Lecithin is fairly sensitive getting the proportions right.
· Lecithin is better at water in oil emulsions, as opposed to your sauce, which is an oil in water emulsion.
You want an emulsifier that is good at making oil-in-water emulsions, is neutral tasting, insensitive to hot and cold, is not finicky in proportions, and easy to get.
I asked Chris Young, a barbeque connoisseur and co-author of the Modernist Cuisine cookbook, what emulsifier he would use, and he said propylene glycol alginate (PGA) because it stabilizes and emulsifies at the same time. I think PGA is problematic, because it is one of the few new ingredients that isn’t all-natural. Chris then suggested sodium caseinate (milk protein salts). Casein is interesting, but I haven’t tried it, so I can’t recommend it.
I would use gum Arabic. Gum Arabic is dried tree sap, is all natural, and has been used for centuries. What I really like about gum Arabic is you can make emulsions with it and then dilute those emulsions quickly without breaking them, which is why it was used in soda syrups before they had cheaper alternatives. Chris agreed that Arabic would work. Get it powdered and use about a percent by weight.
For the stabilizer, you definitely want to use xanthan gum. Xanthan is made by microbial fermentation and is cool because it forms a very weak gel that provides powerful stabilization at low concentrations.
As soon as a sauce made with xanthan is stirred or poured, that gel instantly breaks and gets thin. When you stop stirring, it acts like a gel again. Xanthan is the stuff that keeps spices suspended in salad dressings. It isn’t affected much by acids or temperature, and is easy to work with. The problem with Xanthan is, if you use too much, your sauce will look and feel like snot. Try to use less than 2 grams of xanthan per liter of sauce. Start with 1 gram per liter. If you need more stabilization, add a bit more.
Hot Buttered Rum: This drink is made with the same emulsifier/stabilizer system that I'm recommending for the sauce (Ticaloid 210S) and it works hot or cold.
Question Three: I'm gluten-free and am overwhelmed by the number of flour blends for baking and for cooking. Any ideas/tricks for a reliable and flavorful recipe?
Dave Arnold: There is a bewildering array of gluten-free mixes because no one mix can be a perfect substitute for wheat flour. Different traditional recipes rely on different aspects of wheat — its taste, its protein components (including the oh-so-functional but problematic glutens), its starch components, etc. Depending on what wheat properties a recipe requires, different substitutes are called for. The less important wheat gluten is to a recipe, the easier it is to make a substitution. Cookies and pie crusts don’t rely much on gluten, so those recipes are fairly easy to convert to gluten-free.
If you are converting a recipe that relies on gluten, your mix will need a gluten substitute. The best is xanthan gum. For an explanation of xanthan see question number two. Most sources say to use about half a teaspoon of xanthan per cup of gluten free flour. Some people suggest using guar gum (which comes from ground up seeds), but I disagree. Unless you buy fancy flavor-free guar (from TIC Gums, see above), guar has a terrible beany taste. Guar also just thickens, instead of creating a structure-forming pseudo-gel like xanthan does. You can buy xanthan at Whole Foods.
After you take care of substituting for gluten, you have to substitute for starch. Many gluten-free blends are rice based, because white rice flour is fairly bland; but it can be gritty, is low in protein, and doesn’t really work as a direct wheat-starch substitute. That is why other flours are added –to make it act more like wheat, or to add protein for nutrition, etc.
When you enter the world of gluten-free cooking you have to become a recipe developer. That means keeping good records. Always write down the recipes you use, how they were done, what brands you use, etc. You are going to go through a lot of trial and error, but if you keep accurate records, you will be able to re-create your successes. Nothing is more frustrating than making something incredible but not being able to recreate it.
Since I don’t do much gluten-free cooking, I don’t feel qualified to make specific suggestions, but for a decent run down on the choices, see here.
See you next week. Have questions for Dave? Send them in.